Off-highway vehicles (“OHVs”), such as mining vehicles used to haul heavy payloads, typically employ motorized wheels for propelling or retarding the vehicle in an energy efficient manner. This efficiency is typically accomplished by employing a large horsepower diesel engine in conjunction with an alternator, a main traction inverter, and a pair of wheel drive assemblies housed within the rear tires of the vehicle. The diesel engine drives the alternator and the alternator, in turn, powers the main traction inverter thereby supplying electrical power having a controlled voltage and frequency to electric drive motors of the wheel drive assemblies. Each wheel drive assembly houses a planetary gear transmission that converts the rotation of the associated drive motor energy into a high torque, low speed rotational energy output which is supplied to the wheels.
Planetary gear transmissions are generally operated in a wet lubricated condition. As will be appreciated, it is generally desirable to minimize or prevent leakage of lubricants, e.g., oil, from wheel drive assemblies as such leakage leads to vehicle downtime for disassembly, inspection and repair.
In particular, OHV wheel assemblies typically include torque tubes to facilitate torque transfer to the wheels of the OHV. Torque tubes are generally secured to a body portion of an oil seal by an interference fit, i.e., a fastening achieved by friction between the parts. For metal parts in particular, the friction that holds the parts together is often greatly increased by compression of one part against the other. As such, interference fits are often used for releasably securing parts in an essentially permanent fashion that, once established, is not dependent on fasteners.
Interference fits, however, rely upon compressive stresses in the fitted interference surfaces and, as a result, stress profiles superimposed on those surfaces during torque transfer can periodically partially relax an interference fit. Repeated partial relaxation and re-establishment of an interference fit could potentially, over time, adversely affect the interference surfaces resulting in a gap between the surfaces sufficient for leakage of oil.
In view of the above, it is desirable to provide a torque tube in which cyclic torsional loading does not adversely affect the interference fit between the torque tube and an oil seal attached thereto. It is also desirable to provide a torque tube that is easily and inexpensively manufactured.